I’ve been using the F-6 fixer formula, with half the recommended amount of alum, for a long time. I like it because I can barely smell it. I’ve read that prints will tone & wash better without any hardener. So I’ve mixed the last few batches with no alum, with no ill effects so far. The prints seem to tone the same, though it’s hard to say since each image tones differently and I have not done a real test. Interested in what others thoughts are on using fixer without hardener.